Python Simulations of Chemistry Framework

Outline

  1. What is PySCF?
  2. Feature Highlights
  3. How does PySCF connect to other (CCQ) projects?
  4. Installation
  5. Open-source community and documentation

What does PySCF do?

Mostly generic two-body Hamiltonians: \[ \hat{\text{H}} = \sum_{pq} h_{pq} \hat{a}_p^\dagger \hat{a}_q + \sum_{pqrs} V_{pqrs} \hat{a}_p^\dagger \hat{a}_q \hat{a}_r^\dagger \hat{a}_s \]

Special forms (e.g. sparsity of V) are rarely exploited.

PySCF calculates \(h_{pq} \) and \( V_{pqrs} \) or users can provide them

Several basis options: Gaussian-type orbitals (GTOs) for molecules and solids and plane-wave

What does PySCF do (pt. 2)?

  • Energies (ground and excited state)
  • Forces and geometry optimization
  • Response properties (e.g. dipole moments)
  • Growing support for spectroscopic properties
  • Relativstic effects and non-collinear spins
  • Users can study systems at many levels of theory

Design Philosophy

A sandbox, but a performant one Python user interface with a C back-end 
-------------|----------------------------------------------------
Language     |  files          blank        comment           code
-------------|----------------------------------------------------
Python       |    742          33356          42117         170260
C            |     65           2888           2825          41259
Lisp         |      5             78            145            886
C/C++ Header |     18            176            250            640
CMake        |     12             68            203            268
Fortran 90   |      2             60             56            159
Bourne Shell |      5             20             25             81
-------------|----------------------------------------------------
SUM:         |    851          36652          45628         213574
-------------|----------------------------------------------------
Since inception, our goal has been to treat molecules and solids on equal footing

Correlated Methods

We have a lot of correlated methods that work well in molecules and solids

Xiao Wang

And now... plane waves

Hongzhou Ye and Verena Neufeld

Custom Hamiltonians

h1 = numpy.zeros((n,n))
for i in range(n-1):
	h1[i,i+1] = h1[i+1,i] = -1.0
h1[n-1,0] = h1[0,n-1] = -1.0
eri = numpy.zeros((n,n,n,n))
for i in range(n):
	eri[i,i,i,i] = 2.0

mf = scf.RHF(mol)
mf.get_hcore = lambda *args: h1
mf.get_ovlp = lambda *args: numpy.eye(n)
mf.kernel()

mymp = mp.MP2(mf)
mymp.kernel()

mycc = cc.CCSD(mf)
mycc.kernel()

mycas = mcscf.CASSCF(mf, 4, 4)
mycas.kernel()

MPI4PySCF

Interfaces with PySCF

DMRG
Block (Chan)
CheMPS2 (Wouters)
Selected CI
Arrow (Umrigar)
Dice (Sharma)

QMC
AFQMC (Morales/Zhang)
QMCPACK (LLNL)
NECI (Alavi)
Hande (Thom)
NN VMC
FermiNet (Deepmind)
DeepQMC/PauliNet (Noe)
NetKet (Carleo)
Quantum Computing
OpenFermion
Qiskit (IBM)
OpenQemist (1Qbit)

Somewhere in the future?
ITensor, TRIQS, your research code!

How can I get PySCF?

Option 1: Using pip


								pip install pyscf

Option 2: Using pip to installing the latest version

pip install -e git+https://github.com/pyscf/pyscf.git

Option 3: Build PySCF from sources

Requirements:

  • C and Fortran Compiler
  • BLAS
  • CMake
  • Python 3, NumPy, SciPy, h5py
git clone https://github.com/pyscf/pyscf.git
cd pyscf/pyscf/lib
cmake -B build
cmake --build build --parallel

Documentation

Documentation

Examples

Over 350 examples!!

Open Source Community

Impact

HF
MP2
CCSD
CASSCF
DFT
GW
TDDFT
EOM-CCSD
MRPT
ADC
FCI
X2C
MUCH MORE!
  • Multiple levels of theory to calculate properties
  • If you see something you want and it's not in PySCF already, talk to me!
  • Check out the PySCF channel on the CCQ slack
  • Let us know if you want to get involved!
  • Hackathon for CCQ codes to accelerate interfaces?!?

EXTRA SLIDES

Capabilities in Detail